None of that = stunted. If a breeder doesn't cull their fish they can end up with small poorly shaped specimens that were raised and fed the exact same way as others. Same as with other fish. You see it a lot with angels too.
I consider stunting being due to water quality and feeding, not genetics. As common as discus are now a lot of people sell what should have been culls.
And I'm aware that it's fairy easy and cheap to find nice discus, especially online, but for most people they won't be available locally that often. I've seen well bred healthy discus in this whole region all of a few times. The majority of fish stores are still ordering from major suppliers like Segrest, and their discus quality is highly variable.